Ever-increasing numbers of people have jobs which require them to work long hours at a desk or other work surface. Many conventional desk chairs are designed to be comfortable when the person sitting in them is in an upright position and to tilt back so the person can relax back from time to time to rest, but when the person leans forward in such chairs, the front of the seat presses into the backs of his or her thighs, and the entire posterior is no longer comfortably supported.
Recently, the need to make office seating, especially the category of office seating sometimes called operational seating, more comfortable in a leaning-forward posture has become more widely recognized, and operational chairs which tilt forward are now on the market. Among them are the highly successful "Vertebra" chairs which have seat mounting mechanisms embodying the invention of U.S. Pat. No. 4,131,260.